| In this paper, anaerobic biological process and alcohol precipitation after cationexchange resin pretreatment will be used to remove the pectin in the orangeCan-processing wastewater. Anaerobic biological method is using pectin as carbonsource in a small fermentation device during the anaerobic treatment of pectin inwastewater. The method of cation exchange resin pretreatment-alcohol extract ofpectin in wastewater is based on the characteristics of pectin molecules which arenot soluble in alcohols. In this research, isopropanol and ethanol were used toextract pectin.Anaerobic biological process was used to treat pectin wastewater withacclimated sludge. The effects of the influent pectin concentration and degradationtemperature were investigated, and the intermediate products in pectin degradationwere measured. The results showed that the acclimated sludge can treat pectinwastewater with pectin concentration over3000mg·L-1and its removal efficiency ofpectin and COD were both greater than90%. Compared with the unacclimatedsludge, the results showed that by using acclimated sludge, pectin removalefficiency increased by59.2%. The degradation rate increased when the influentpectin concentration was increased. The COD removal efficiency was relatively low(41.6%~82.0%), when the influent pectin concentration was less than500mg·L-1.But the COD removal efficiency could mantain above91%when the influent pectinconcentration beyond1000mg·L-1. The higher the temperature was, the shorter thetime was needed for pectin degradation. After144h of anaerobic degradation, thepectin concentration of enfluent water was2589.6mg·（L·h）-1when the temperaturewas5℃. But the pectin concentration was less than80mg·L-1only after36h ofanaerobic degradation when the temperature was35℃. The COD removal efficiencyof anaerobic sludge for pectin wastewater increased from38.6%to91.5%when thetemperature ranged from5℃to35℃, but gradually dropt when the temperaturebeyond35℃. The main intermediate products in pectin degradation were supposedto be acetic acid, propionic acid, lower ester, and alkyl alcohol (C12-C40).Alcohol precipitation after cation exchange resin pretreatment process was usedto treat pectin wastewater. The effects of the precipitation pH, time, temperature,and alcohol-liquid ratio were investigated. The results showed that at pH3and4, when isopropanol and ethanol were used to extract pectin from the wastewater in theorange Can-processing, the precipitation efficiency were the highest. Pectinprecipitation mainly occurred in the first30min. When the temperature was higherthan95℃, the yield rate of pectin extracted with isopropanol and ethanol decreasedobviously. The pectin yield rate increased with alcohol liquid ratio enhanced, whenalcohol-liquid ratio is lower than11:10. While pectin yield rate decreased little,when the alcohol-liquid ratio is higher than11:10. During the porcess of alcoholprecipitation after cation exchange resin pretreatment to treat pectin in thewastewater, the importance of each factor which affected the yield of pectin were asfollow: alcohol-liquid ratio> pH> precipitation temperature> precipitation time. Theoptimum extraction conditions were: precipitation pH of4, precipitation time of45min, precipitation temperature of25℃, alcohol-liquid ratio of11:10.In alcohol precipitation after cation exchange resin pretreatment to treatmentpectin was used to treat pectin wastewater, the effects of this pretreatment wereinvestigated. The results showed that when cation exchange resin pretreatment wereapplied, a higher removal efficiency could be achieved than directly precipitationwith alcohols. Pretreatment time showed little effect on the removal efficiency ofpectin, but pretreatment pH has a greater impact. The pectin removal efficiencyincreased with the pH enhanced from1to3, but decreased gradually from3to6. Byusing alcohol precipitation after cation exchange resin pretreatment to treat pectinwastewater removal efficiency of COD can reach90%, when the initial pectinconcentration was4000mg·L-1. |
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